Igniting-plug.



-- No. 690,640. l Pafented 1an. 7, |902".

L H. nAvls & E. n. MELLEN.

IGNITING PLUG.

(Application 1 ed July 28, 1900.; (N o M miel.)

@ggf 'Wif #mls Ferias co.. vHuTuLmm.. wAsnmmon. D- c UNITED STATES ISAAC l-I. DAVIS, OF BOSTON, AND EDWIN D. MELLEN, OF CAMBRIDGE,

. MASSACHUSETTS.

lGNlTlN G-PLUG.

' SPECIFICATION forming part of Letters Patent No. 690,640, dated January 7, 1902.

Application filed July 28, 1900.

To all whom, it may concw'n: l

Be it known that we,IsAAC H DAVIS, of Bos- -ton, in the county of Suffolk;` and EDWIN D.

MELLEN, of Cambridge, in the county of Middlesex, in the State of Massachusetts, have invented certain new and useful Improvements in Igniting-Plugs, of which the following is a specification.

This invention relates to plugs employed in igniting devices of the jump-spark class for explosive engines. The invention particularly depends for its novelty on the use of a tapered insulatingpiece or plug employed in the igniting-plug, whereby the device is simplified and breakage is less likely to occur. In plugs as heretofore constructedconsiderable difficulty is experienced by the breakage of tho central insulating piece. These plugs are commonly constructed with a socket which screws into the engine-cylinder and a porcelain insulating-piece which is provided with an enlargement or boss at or near its center, which is held to a shoulder on ametallic case, usually with a packing, by

means ofa metallic nut screwed into the case. Breakage of the porcelain piece takes place on account of the unequal expansion of its different portions due to the heat of the combustionchamber,and sometimes because the retaining-nut which holds the porcelainpiece in the case is screwed down too hard against the shoulder on the saidporcelain piece. Our improved construction entirely does away with this faulty construction and the difficulties attending its use.

Of the accompanying drawings, Figure 1 represents a side elevation of an igniting- SerialNo. 25,082- (Ne model.)

the explosive-engine, the body portion of the socket being preferably formed externally to receive a wrench or similar tool. An electrode 4 is fixed to the inner end of the socket 1, which latter is grounded through the engine-frame.

The socket l is provided with a longitudinal frust'o-conical bore, in which is iitted a frusto-conical insulating-plug 6, made of a suitable refractory material, such as lava or its equivalent. The plug 6 and its seat with- 4in the socket 1 are made to correspond exactly in shape, so as to secure a gas-tight it. The plug may be driven into the socket to a tight fit, which entirely avoids the use of packing between the plug and socket, such as has heretofore been employed.

7 is the other electrode, between which and the electrode 4 the spark occurs. The electrode 7 is provided with a screw-threaded nal aperture 9 in the plug 6, and on the outer end of said stern is screwed a nut 1.1. nut bears against a cup shaped collar 10, whichincloses the projecting outer end of the plug 6 and rests upon the outer end of the socket l. The collar 10 is also made of insulating material and is formed with an aperture 14, through which the stem 8 projects. The nut 11 has a threaded shank 12, upon which a thumb-nut lscrews, the two nuts forming a binding-post for securing the circuit-wire 17. The electrode 7 is formed as a head on the stem 8, which acts as a shoulder bearing against the inner end of the plug 6. When the nut 11 is screwed down against the collar 10, the plug 6 is then held against any tendency to be jarred or shaken from its seat -in the socket. The outer end of the plug 6 projects a considerable distance beyond the outer end of the socket l in order to sheath the electrode-stem and preventthe possibility of a short circuit between it and the socket. This necessitates making the collar 10 of a cup shape in order to interpose an abutment between the socket 1 andthe nut screwed on the outer end of the electrode-stem.

We have found in practice that a tapered insulating-plug of substantially the character described and mounted in the manner which stem 8, which extends through a longitudi- Said IOO

we have indicated is much more durable than the hereinbefore-described form. of plug in use prior to our invention.

Fig. 4 represents a modified form of the plug 6, in which the inner portion l5 only of the plug is tapered, Whilethe outer portion 16 is substantially cylindrical. This form of plug fits in a metallic socket of corresponding form.

It will be noted that the vitreous plug or core 6 is characterized by the absence of abrupt projecting` shoulders or flanges abutting against any part of the socket l or subject to the heat of the cylinder or combustion-chamber. Former cores of igniting plugs have been subject to fracture not only on account p of their having such shoulders located in positions Where they Would be forced against an unyielding surface by the explosions within the engine-cylinder, but also because of the ununiform and badly-distributed expansions and contractions of a shouldered plug under the influence of its changes in temperature. These causes produce transverse cracks in the plug, usually at the point Where the flange or shoulder juts from the body of the plug. A deposit of carbon is then gradually made in this fracture and the plug becomes useless from short-circuiting.

We claiml. An igniting-plug comprising a metallic casing having an aperture with an elongated slight taper formation, a vitreous core characterized by the absence of abrupt projecting shoulders or flanges and having an elongated slight taper formation complemental to that of the casing aperture and fitting closely therein and projecting beyond the smaller end of the casing-aperture, a cup-shaped insulating-collar inclosing the projecting end of the core and bearing on the casing around the core, an electrode passing through said core and collar, and a nut screwed on the upper end of the electrode and bearing on the collar to retain the latter and the core and the electrode in their proper relative locations.

2. An igniting-plug for explosive-engines, comprising a metallic socket formed for attachment to the engine, a refractoryinsulating-plug seated in said socket and its outer end projecting beyond the outer end of the same, an electrode engaged with the insulating-,plug and having a threaded stem projecting beyond the outer end thereof, a cupshaped insulating-collar inclosing the projecting end of the plug and bearing against the outer end of the socket, and a nut screwing on the stem and bearing against the collar, whereby the plug is held to its seat in the socket.

In testimony whereof We have afxed our signatures in presence of two witnesses.

ISAAC H. DAVIS. EDWIN D. MELDEN.

Witnesses:

C. F. BROWN, A. D. HARRISON. 

